The signature is a small cost for a user, but it wont cover your expenses.

The seed investors already have data on users email, their address, their school, their credit card number plus much much more.

What they dont have yet is users blockchain data, and to link the data they need apps like Partiko. They wont pay you for something that is already publicly available on the Steem blockchain.

I just hope Partiko wont become a tool for the bad actors thats all.